Until recently emphasis on IT-infrastructure laid on performance. Only from 2006 
research started to be conducted on how to make it more energy
efficient~\citep{ieee802.3az}.
To make an effort to also use current infrastructure in a more efficient manner, there
is need to map energy profiles of devices. On the basis of those profiles decissions
can be taken towards whether or not, or when certain infrastructure is to be used.

\section{What is energy profiling?}
An \emph{energy profile} is a collection of energy related properties of devices.
Within the scope of IT-network infrastructure energy profiling can be described as the
extension of currently available performance metrics by including metrics that take
into account energy consumption of devices. \\
These metrics can be used to generate a per device energy profile providing
information on the energy efficiency under different circumstances. For a computing
device e.g. the power consumption will rise, when the CPU load is high.
Furthermore the energy profiles can be taken advantage of for networking path
decisioning.

\section{Why is it needed?}
Since at least 2009 there is official scientific consensus that climate change by the
amplification of greenhouse gas (GHG) emissions is anthropogenic~\citep{EOST:EOST16685}.
Therefore steps need to be taken to reduce the emissions wherever possible. \\
Power consumption of the Internet in 2010 represented between estimated 1.1 and 1.9\%
of the global energy consumption~\citep{emergy}. In absolute terms this is between 170
and 307GW. As a lot of the currently operating infrastructure was build with providing
performance in terms of speed, but not with energy savings, there is a lot to win.

\section{What are current restraints?}
The main restraints in applying energy profiling to save energy are the lack of
standard in both data representation and normalization as well as the lack of sensors
in deployed hardware. The first results
in administrative limitations, as too much manual intervention is needed to gather
energy data at all. Hardware vendors partly implement sensors and interfaces to
present the readings, but not in a standardized manner. To perform data gathering on a
wide range of devices the variety of different vendor approaches has to be taken into
account. This results in too big of an effort.
The current methods to gather energy data at all are presented hereunder.
\begin{description}
	\item[SNMP] \emph{Simple Network Management Protocol} is a protocol that
allows to manage devices through the network. It uses \emph{Management Information
Bases} (MIBs) as extensible means to define the variables that will be exposed by the
device. A wide variety of MIBs has been defined, amongst which some that contain
energy metrics. Unfortunately (<- please change, not scientific) the definition alone
does not mean that it is implemented nor implementable in all devices. 
	\item[PDU] A \emph{Power Distribution Unit} is a device that distributes power
to a number of devices. Most PDUs have a more advanced set of functions, amongst which
the availability to expose the energy consumption per outlet. Racktivity devices for
example can be read out through an \emph{Advanced Programming Interface} or
\emph{Application programming interface} (API). The presented readings and the APIs
differ per vendor, whereas there is no standard.
	\item[CLI] Network hardware vendors often equip their devices with a 
\emph{Command-line interface} as means of configuring and (basic) monitoring of the
device. Some vendors make accessible the sensor-readings of devices by CLI-commands.
Unfortunately (<- please change, not scientific) neither the CLIs itself, nor the
CLI-command to show the readings, nor the way the readings are presented, are
standardized.
\end{description}
Furthermore there are data sharing limitations, as nor protocol nor infrastructure is
in place to spread the data across domain-boundaries. 

\section{How can above mentioned problems be overcome?}
To overcome the above mentioned constrains, standardization has to be introduced on
several layers. Chapter~\ref{sec:metrics} aims at providing the base for a standard
by defining a metric that is as independent as possible from the mentioned
limitations.
